Check out Dancing Dots. Http://www.dancingdots.com
They offer low vision and braille options for reading, composing, scanning and reading music in various formats as well as software, assistive technology and training.

This probably already occurred to you, but I will suggest it just in case. You might also want to try posting your question on Applies. The site focuses on accessibility of applications for people who are blind and use Mac OS or iOS. For applications that work on Windows, you might try posting to screen reader specific forums. I think there are forums and e-mail lists for all the major Windows screen readers. Even if you don't find an accessible application, you might be able to contact some musicians who are blind using that approach and they might be able to share what they do--which might be approaches that can be used until you can locate something that is accessible.